Question

find the sum of first 85 odd number and even number ..

Answer 1

Sum of first 85 terms of the odd numbers is 7225 and even numbers is 7140.

• Odd numbers starts with 1, first term(a) will be 1 and common difference(d) will be 2 as the series of odd numbers is 1,3,5,7,9 and so on.
• Sum of 85 terms of his AP will be

Sum = $\frac{n}{2} [2a + (n-1)d]$

Sum = $\frac{85}{2} [2 + 84*2]$

Sum = 7225 (odd terms)

• Now sum of 85 even terms-

• Even numbers starts with 0, first term(a) will be 0 and common difference(d) will be 2 as the series of odd numbers is 0,2,4,6,8 and so on.
• Sum of 85 terms of his AP will be

Sum = $\frac{n}{2} [2a + (n-1)d]$

Sum = $\frac{85}{2} [0 + 84*2]$

Sum = 7140 (even terms)